This invention relates to a hydraulic brake booster. Such boosters generally use pressurized fluid developed by a vehicle's power steering pump to provide a power assist to the vehicle master cylinder when the brakes of the vehicle are applied. If the power steering pump ceases to operate, a hydraulic reserve system is provided to supply pressurized fluid to the booster.
It is well known in the art to provide an accumulator which is charged during normal operation of the power steering pump for supplying pressurized fluid to the booster.
The weight of a motor vehicle generally determines the size or capacity of the brake booster, which must provide sufficient power assistance during braking. Correspondingly, the capacity of the hydraulic reserve system or accumulator is also dependent on the weight of the motor vehicle, for the accumulator must also provide a sufficient power assist to effectuate braking.
With one size of brake booster housing it is possible to vary the power assistance by varying the diameter of a piston, which is slidably disposed within the brake booster housing. Therefore, with one size of brake booster housing it is desirable to provide a hydraulic reserve system, which system is suitable for various sizes of pistons to provide the necessary power assistance when the steering pump ceases to operate, regardless of the power assistance required by the weight of the motor vehicle.